98runner210

I have fog lights. They are wired directly from the battery to a toggle switch. They are not tied into the headlights or ignition in any fashion. They are grounded to the bumper where they mount. Anytime I turn them on my gas gauge goes down by about a quarter of a tank. If I turn them off it goes back up. I have a new alternator and it did it with th old one too. WTF?

ETRNL

bad ground.. ground them to the frame or directly to the battery

NorCalWheeler

I have some Fog lights that I wired with a wiring kit from Autozone and it was really easy, I would probaly suggest that. I know a little bit about wiring so with that little knowledge i would say it's probably not a ground unless the gas gauge is grounded to the bumper which i really doubt, but thats just my two cents.

SoCalPaul

Auxiliary lights should be wired using a relay. The inside switch should activate the relay to supply power to the lights. Using the switch for activating the lights directly can cause various problems. The lights should be grounded near or to the battery ground.

4runnermt

+1, w/o a relay its also a potential fire hazzard!

ETRNL

+2 good catch! you defiantly dont want all of that wattage going through your switch

98runner210

The last setup had a relay with similar results. I will try re-grounding. How would I setup the wiring to include a relay?

Yoda

Relay = yes

But, also run a better ground wire from your body/frame to your battery negative.

Gerdo

IF the wire and switch are a high enough rating AND you do have a proper size fuse (as close to the battery as possable) you don't NEED to use a relay. A relay will allow you to run a lower amperage thru a thinner wire and lower amp switch. Even with a relay you MUST fuse it.

Run a ground wire to the body. The bumper mountings are pre-painted and do not allow for a good ground.

ETRNL

just like this.... but u can substitute the "+12v from low beams" for
a +12v

ETRNL

my bad double post..

corax

x2 on cleaning or putting in a better ground from the battery to the body and frame

mt_goat

Here's some more on relays http://www.bcae1.com/relays.htm

98runner210

where is the factory grounds at? i want to check them and maybe scuff them up a bit. Why wouldn't the bumper be a good ground? it is chrome and goes directly to the frame.

nv4runner

It sounds to me like you have a bad case of mutual induction. Current, or amps, flowing through a conductor creates a magnetic field and it is interfering with the signal for your gas gauge. You should definitely wire it up with a relay, but also try rerouting your wires under the dash so they do not parallel other wires. That is why some wire harnesses are twisted when you take them apart. This keeps the magnetic field from creating interference in other wires.

Gerdo

Between the nice highly conductive chrome bumper and the frame are a couple of painted/coated mounts. Also I believe that the frame on 3rd gens don't have a direct ground wire (battery to body and body to engine only)

You're probably getting a ground thru the fuel lines and sending some voltage to the fuel sending unit.

Run a ground wire to a bolt on the body and you should be good.

98runner210

Ok i will get some good gauge wire and shrinkwrap and see whats what.

mt_goat

Good advice. When I was trying to trouble shoot a CB buzz I added a 12 gauge ground from my frame to my body, it didn't help but I left it and now it helps ground some rock lights I have mounted on the frame. It never hurts to have redundancy with grounding too. My truck didn't have any ground between the frame and body that I could see. The body mounts are kind of isolated from current flow it appears.

JamesD

Sounds like the wires to your switch is too close to the instrument cluster.

James

98runner210

its a factory switch in the factory location. I am thinking it has to do with the ground too.